Immunosuppression and tumor escape from immune recognition are thought to be major factors responsible for the establishment and progression of cancer. A number of factors responsible for the suppression of NK cell cytotoxicity in humans have been identified previously. However, the significance and the precise mechanism of this suppression induced during the interaction of NK cells with either tumor cells or healthy primary cells are not well understood. It is shown that freshly isolated tumor infiltrating NK cells are not cytotoxic to autologous tumors. Moreover, NK cells obtained from the peripheral blood of patients with cancer have significantly reduced cytotoxic activity. In addition, NK cell cytotoxicity is suppressed after their interaction with stem cells. However, interaction of NK cells with the resistant tumors does not lead to suppression of NK cell cytotoxicity.
Many mechanisms have been proposed for the functional inactivation of tumor associated NK cells including the over-expression of Fas ligand, the loss of mRNA for granzyme B and decreased CD16 and its associated zeta chain.
Many metastatic tumor cells exhibit constitutively elevated NFκB activity. Increased NFκB activity is shown to have a causal relationship to neoplastic transformation, and uncontrolled cell growth in many cell types. Human solid tumors exhibit constitutively activated NFκB.
We have previously shown that NK resistant primary oral keratinocyte tumors demonstrate higher nuclear NFκB activity and secrete significant levels of Granulocyte Monocyte-Colony Stimulating Factor (GM-CSF), Interleukin (IL)-1β, IL-6 and IL-8. Moreover, the addition of Non-steroidal anti-inflammatory drugs (NSAIDs) which inhibit NFκB have the ability to reverse immunosuppression induced by a tobacco-specific carcinogen in addition to their well-established ability to decrease oral dysplasia as well as induction of overt cancer in transgenic animals. In agreement, we have previously demonstrated that inhibition of NFκB by Sulindac treatment of tumor cells increases functional activity of NK cells. In addition, targeted inhibition of NFκB in skin epithelial cells resulted in the induction of auto-immunity and inflammation.
The exact mechanism by which NFκB nuclear function in oral keratinocytes modulate and shape the function of key interacting immune effectors is yet to be determined. We have previously shown that inhibition of NFκB by the IκB super-repressor in HEp2 tumors leads to significant increase in cytotoxicity and secretion of IFN-γ by the human NK cells. However, neither the underlying significance nor the physiological relevance of NFκB modulation in tumors or in primary cells responsible for the alteration of NK cell cytotoxic function have been addressed or studied previously. It is clear that the objective in cancer is to enhance the function of cytotoxic immune effectors and in auto-immunity and inflammation the aim is to inhibit immune effector function. Therefore, dissection of the underlying mechanisms of immune activation when NFκB is modulated in the cells might help design strategies to target each disease accordingly. Indeed, targeted inhibition of NFκB function in both the intestinal epithelial cells and the myeloid cells was previously shown to result in a significant decrease in the size and the numbers of the tumor cells.
Regenerative medicine is the process of creating living, functional tissues to repair or replace tissue or organ function lost due to age, disease, damage, or congenital defects. This field holds the promise of regenerating damaged tissues and organs in the body by introducing outside cells, tissue, or even whole organs to integrate and become a part of tissues or replace whole organ. Importantly, regenerative medicine has the potential to solve the problem of the shortage of organs available for donation compared to the number of patients that require life-saving organ transplantation.
One key to the success of regenerative medicine strategies has been the ability to isolate and generate stem cells, including pluripotent stem cells. In one aspect, pluripotent stem cells can be differentiated into a necessary cell type, where the mature cells are used to replace tissue that is damaged by disease or injury. This type of treatment could be used to replace neurons damaged by spinal cord injury, stroke, Alzheimer's disease, Parkinson's disease, or other neurological problems. Cells grown to produce insulin could treat people with diabetes and heart muscle cells could repair damage after a heart attack. This list could conceivably include any tissue that is injured or diseased.
The generation of pluripotent stem cells that are genetically identical to an individual provides unique opportunities for basic research and for potential immunologically-compatible novel cell-based therapies. Methods to reprogram primate somatic cells to a pluripotent state include differentiated somatic cell nuclear transfer, differentiated somatic cell fusion with pluripotent stem cells, and direct reprogramming to produce induced pluripotent stem cells (iPS cells) (Takahashi K, et al. (2007) Cell 131:861-872; Park I H, et al. (2008) Nature 451:141-146; Yu J, et al. (2007) Science 318:1917-1920; Kim D, et al. (2009) Cell Stem Cell 4:472-476; Soldner F, et al. (2009) Cell. 136:964-977; Huangfu D, et al. (2008) Nature Biotechnology 26:1269-1275; Li W, et al. (2009) Cell Stem Cell 4:16-19).
A significant first hurdle in stem cell-based therapy is the differentiation of pluripotent cells into a desired tissue type. Such methods currently rely on the step-wise introduction of factors and conditions to guide the cells down a developmental pathway, resulting eventually in a mature or committed progenitor cell that can transplanted into a patient.
Embryonic stem cells (ESCs) are an attractive source for tissue regeneration and repair therapies because they can be cultured indefinitely in vitro and can be differentiated into virtually any cell type in the adult body. However, for this approach to succeed, the transplanted ESCs must engraft successfully and survive long enough to permit a therapeutic benefit. An important obstacle facing the engraftment and function of hESCs is transplant rejection by the immune system. The present invention addresses this issue.